18mm sight glass replacement?

[jatgm12]

So to replace the sight glass am I to understand that I need epoxy? I ordered replacements that appear to have the metal bit with the glass too that were 18mm on Amazon and they came with o rings, so is it possible to just use the oring? Are they all the same? All the YouTube videos I found seem to say to use a bit of calking and a c clamp, I was hoping to avoid even taking it off the bike so I don't have to bleed the thing again.